The Ten Sefirot: Divine Emanations
Yesod is the ninth of the ten sefirot, and the sixth of the emotive attributes within Creation.
Yesod appears in the configuration of the sefirot along the middle axis, directly beneath tiferet, and corresponds in the tzelem Elokim to the procreative organ (in the male; in the female, to the womb).
Yesod is associated in the soul with the power to contact, connect and communicate with outer reality (represented by the sefirah of malchut). The foundation (yesod) of a building is its "grounding," its union with the earth (malchut).
Corresponding to the procreative organ of man, yesod is the foundation of generations to come. The power to procreate is the manifestation of infinity within the finite context of the created human being. Each individual man is "small" relative to all generations to come (from him). The yesod is referred to as the "small limb" of man, the "small that holds the large [infinite]." The yesod is the "small" and "narrow" bridge between the infinite potential of procreation that flows into it and its actual manifestation in the progeny of man.
For this reason, the sefirah of yesod is identified in the Torah with the tzadik (righteous one), as is said: "and thetzadik is the foundation of the world." In particular, this refers to the one, perfect tzadik of the generation. In the very body of the tzadik, finite and limited in time and space, God's infinite light and creative lifeforce becomes manifest. The tzadik procreates on the spiritual plane as well as on the physical plane. He experiences procreation in the inner eye of his consciousness, in the continual flow of new insights and true innovations in Torah. He procreates by arousing the souls of his generation to return to God and the Torah. And so did Rabbi Shneur Zalman of Liadi say, with regard to the first mitzvah of the Torah ("be fruitful and multiply")–the "foundation" of the Torah: "A Jew must make another Jew."
The yesod is also referred to as the brit, the holy sign of the covenant (that God made with Abraham, the first Jew). In particular, the yesod is the covenant between the two Divine attributes of truth and peace, as the prophet says (Zacharia 8:19): "and truth and peace shall love." The origin of love is represented by the soul of Abraham, of whom is said "Abraham, My lover" (Isaiah 41:8). All of his lovingkindness (chesed) flows down (as water) to become concentrated in yesod. There it creates the covenant between the absolute truth of Torah and the peace of mitzvot, good deeds performed with love for Israel.
Just as "foundation" implies "beginning," so is yesod called "the conclusion of the body" (for the body, tiferet, extends until the procreative organ, yesod, as is said: "body and brit are considered one"). The property of "peace"–shalom–inherent in yesod means as well the power to bring an act to its conclusion, as our sages teach us: "one who begins a mitzvah, is told 'finish'." Thus, the full sense and power of the sefirah of yesod is its ability to manifest the union between beginning and end, as is said in Sefer Yetzirah (1:7): "the end is enwedged in the beginning, and the beginning in the end."
Yesod = 80 which equals 8 (chet) times 10 (yud)–chai. The tzadik is called chai. 80 = klal (the "general" or "entire" body of the Jewish people). The klal, the tzibur ("entire community") "never dies." The tzadik yesod olamis the "general soul" (neshama klalit) of the generation.
The six sefirot from chesed to yesod join and develop to form the partzuf of Zeir Anpin. Zeir Anpin receives its "head" or "brain-power" (the three higher sefirot of chochmah binah da'at) from the higher partzufim of Abba andImma.
The spiritual state identified in Chassidut as corresponding to the sefirah of yesod is that of emet (truth), in the sense of the power to "verify" one's convictions and emotions in action and to achieve true self-fulfillment in life.